1. Field of the Invention
The present invention relates to a tire pressure sensing device and a tire pressure sensing method, and more particularly to a wireless tire pressure sensing device and a wireless tire pressure sensing method to facilitate setting and modifying a standard tire pressure of the wireless tire pressure sensing device after the wireless tire pressure sensing device is mounted in a tire.
2. Description of the Related Art
With reference to FIG. 7, a conventional wireless tire pressure monitoring system (WTPMS) has multiple wireless tire pressure sensors 71˜74 and a monitoring unit 70. The wireless tire pressure sensors 71˜74 are respectively mounted in tires of a vehicle. The monitoring unit 70 is mounted inside the vehicle. Each wireless tire pressure sensor 71˜74 has a battery, a sensing element, a control unit with embedded or external memory, a high-frequency transmitting circuit and a low-frequency circuit. Each wireless tire pressure sensor 71˜74 is configured with one set of dedicated code having at least 8 bits when shipped out of the factory.
When the WTPMS is activated, each wireless tire pressure sensor 71˜74 regularly or irregularly transmits detected information and the dedicated codes to the monitoring unit 70 through the high-frequency transmitting circuit by means of a fixed coding method. After receiving data, the monitoring unit 70 compares the received data with the dedicated codes to determine if the received data are transmitted from one of the wireless tire pressure sensors 71˜74 of the vehicle or from other vehicles. After determining that the data are transmitted from one of the wireless tire pressure sensor 71˜74 mounted in one of the tires of the vehicle, the monitoring unit 70 further decodes tire pressure, tire temperature and other detected relevant values of the tire.
Manufacturers normally store standard tire pressure, low pressure threshold, and other relevant threshold values in a memory of the monitoring unit 70 before delivering the WTPMS. Hence, after comparing the received tire pressure and other relevant values with the preset threshold values, the monitoring unit 70 determines if the tire is in an abnormal condition.
Although most WTPMSs store data such as standard tire pressure or threshold values in the memory of the monitoring unit 70, some wireless tire pressure sensors have relevant tire pressure pre-stored prior to delivery so that the wireless tire pressure sensors can intensively transmit data to inform the monitoring unit 70 of variation and irregularity of abnormal tires for alerting drivers ahead of time when the detected tire pressure or other detected values exceed the preset threshold values.
However, tire pressure has not been standardized yet for various vehicles on the road or for sales. Vehicles varying in model, weight or tire type may have different tire pressure values for their tires. For example, certain car owners prefer to replace original tires of their vehicles with high speed tires requiring much higher standard tire pressure than that of the original tires. If the threshold values remain the same, malfunction or misjudgment of the WTPMS easily arises. As a result, when the desired tire pressure is different from the preset tire pressure, service personnel of a service center or a tire store must manually adjust the threshold valves in the monitoring unit 70. As the threshold value calculation method varies from WTPMS to WTPMS and the procedure for adjusting the threshold values in the monitoring unit is complicated, the adjusting procedure is not easy to be correctly conducted.
To cope with the foregoing problems, the tire pressure sensor can be mounted in a tire and wirelessly transmits detected tire pressure values to a master control unit for drivers to understand current tire pressure condition. The master control unit computes an average tire pressure value of the two front wheels and the two rear wheels and stores the value therein as a pressure warning value upon detecting tire pressure of the front wheels and the rear wheels. It is unnecessary for such solution to set up the pressure warning values for different types of vehicle models prior to their delivery. The tire pressure sensors of the solution can be universally applied to any kind of vehicle model or tire.
However, the above solution only tackles the setup issue of the monitoring unit 70 while leaving the setup issue of the wireless tire pressure sensors unresolved.
Additionally, as certain wireless tire pressure sensors are pre-stored with threshold values or standard tire pressure therein and are mounted and sealed in tires prior to their shipment, the threshold values in the wireless tire pressure sensors cannot be adjusted after their delivery. Accordingly, manufacturers of the wireless tire pressure sensors need to produce various wireless tire pressure sensors having different threshold values to meet the need of different threshold values, and inevitably build up the stocking pressure on inventory management for the manufacturers.